@seriousme/opifex/dist/server/handlers/handleSubscribe.js

MQTT client & server for Deno & NodeJS

import { PacketType, } from "../deps.js";
/**
 * @constant {number} SubscriptionFailure
 * @description Code indicating a failed subscription attempt
 */
const SubscriptionFailure = 0x80;
/**
 * Checks if a client is authorized to subscribe to a topic
 * @param  ctx - The connection context
 * @param  topicFilter - The topic filter to check authorization for
 * @returns True if authorized, false otherwise
 */
function authorizedToSubscribe(ctx, topicFilter) {
    if (ctx.handlers.isAuthorizedToSubscribe) {
        return ctx.handlers.isAuthorizedToSubscribe(ctx, topicFilter);
    }
    return true;
}
/**
 * @function handleSubscribe
 * @description Processes an MQTT SUBSCRIBE packet
 * @param {Context} ctx - The connection context
 * @param {SubscribePacket} packet - The SUBSCRIBE packet received from the client
 * @returns {Promise<void>}
 * @throws {Error} If subscription processing fails
 * @remarks The order of return codes in the SUBACK Packet MUST match the order of Topic Filters in the SUBSCRIBE Packet [MQTT-3.9.3-1]
 */
export async function handleSubscribe(ctx, packet) {
    /*
     * The order of return codes in the SUBACK Packet MUST match the order of
     * Topic Filters in the SUBSCRIBE Packet [MQTT-3.9.3-1].
     */
    const validSubscriptions = [];
    const returnCodes = packet.subscriptions.map((sub) => {
        if (ctx.store) {
            if (!authorizedToSubscribe(ctx, sub.topicFilter)) {
                return SubscriptionFailure;
            }
            ctx.persistence.subscribe(ctx.store, sub.topicFilter, sub.qos);
            validSubscriptions.push(sub);
            return sub.qos;
        }
        return SubscriptionFailure;
    });
    await ctx.send({
        type: PacketType.suback,
        id: packet.id,
        returnCodes: returnCodes,
    });
    /*
     * send any retained messages that match these subscriptions
     */
    if (ctx.store) {
        ctx.persistence.handleRetained(ctx.store.clientId);
    }
}
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